Anti-nucleic acid antibodies are involved in the pathologic mechanisms in human Systemic Lupus Erythematosus and the murine models. We have examined the heterogeneity of the anti-nucleic acid antibodies and found antibodies to DNA and Polyadenylic acid to be relatively restricted. We now will study and define the system old idiotype-anti-idiotype interactions of these antibodies. Examination of idiotype and anti-idiotype in serum as well as their role as surface receptors should provide valuable insights into the immunological regulation of anti-DNA and anti-PolyA antibodies. We shall investigate the ability of anti-idiotype antisera to suppress the antibody response to DNA and Poly A.